**1937, Peking. **
By the Marco Polo Bridge, a top-secret file has been kept in dust for fifty years. "I have secrets in my mind, but my name is no longer important" - these are the last words of Shen Zhongming, the platoon leader of the 29th Army, and they are also a mystery that no one has been able to solve for half a century.
**1985, Beijing. **
Lin Xiaoyue, a graduate student in the Department of History, accidentally discovered a top-secret file codenamed "Shadow Seven". Her grandfather's strange reaction, the missing bullet casings in the file, the dead witnesses... All clues point to the same answer: Shen Zhongming is not dead, he just changed his identity and lurked in the darkness.
**From Marco Polo Bridge to Harbin, from 1937 to 1950——**
How many years does it take a person to complete a task? How many secrets does one have to hide to keep a faith?
When the dust of history was uncovered layer by layer, the person called "Shadow" finally walked out of the darkness.
